Dissolved oxygen measuring device
Bases for measurement | 5
B-H86.0.21.DB2-1.0
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5.1.2 Design
Storage bottle
Shaft
Membrane head
Refill opening
Platinum electrode
Platinum electrode
If oxygen is present, it is reduced on the platinum electrode and the sensor delivers a
signal. Soiling on the platinum electrode or between the membrane and electrode can
influence the measurement.
Storage bottle
The storage bottle is provided to keep the membrane moist. The service life of the
sensor is extended as a result. Distilled or deionised water is in the storage bottle; do
not add any other liquids!
Membrane head
The membrane head is covered with a thin plastic membrane. Faulty measurements
will occur if the membrane is damaged or there are large air bubbles or even an air
bubble ring on the membrane. This can also be the cause if a sensor can no longer be
calibrated. The GWOK 02 membrane head is a spare part and can be re-ordered sep-
arately.
Refill opening
Electrolyte must be filled or added for the initial commissioning of a sensor which is
delivered dry, when performing maintenance or after use at high temperatures.
5.1.3 Service life
The sensor signal deteriorates relatively quickly at the end of the service life of the
sensors. The electrode evaluation in %, therefore, can only be used as a guide value.
A value of 70% does not mean that exactly 70% of the service life is still available,
rather that the electrode signal has 70% of a comparison signal.
NOTE
The sensor evaluation is updated by the measuring device after a successfully per-
formed calibration of the oxygen sensor.
The nominal service life can be reduced significantly due to use. Influential factors in-
clude:
– Storage / operating temperature
– Contamination of the measured water
